Objectives: Modified ultrafiltration (MUF) has been shown to decrease the postcardiac surgery inflammatory response and to improve respiratory function and cardiac performance in pediatric patients; however, this approach has not been well established in adults. The present study hypothesized that MUF could decrease the postsurgical inflammatory response, leading to improved respiratory and cardiac function in adults undergoing coronary artery bypass grafting. Methods: Sixty patients undergoing coronary artery bypass grafting were randomized to the MUF or control group (n = 30 each). MUF was performed for 15 minutes at the end of bypass. The following data were recorded at the beginning of anesthesia, end of bypass, end of experimental treatment, and 24 and 48 hours after surgery: alveolar-arterial oxygen gradient, red blood cell units transfused, chest tube drainage, hemodynamic parameters, and cytokine levels (interleukin-6, P-selectin, intercellular adhesion molecule, and soluble tumor necrosis factor receptor). Results: The MUF group displayed less chest tube drainage than the control group after 48 hours (598 ± 123 mL vs 848.0 ± 455 mL; P = .04) and less red blood cell transfusions (0.6 ± 0.6 units/patient vs 1.6 ± 1.1 units/patient; P = .03). Hematocrit level was higher in the MUF group than in the control group at the end of bypass (37.8% ± 1.1% vs 34.1% ± 1.1%; P < .05), but the levels were comparable at 48 hours. Similar values for interleukin-6 and P-selectin were observed at all stages. Plasma levels of intercellular adhesion molecule were higher in the MUF group than in the control group, particularly in the first sampling after experimental treatment (P = .01). Plasma levels of soluble tumor necrosis factor receptor were higher in the MUF group than in the control group at 48 hours. Hemodynamic and oxygen transport parameters were similar in both groups throughout the observation period. There were no differences in other clinical outcomes. Conclusions: Use of MUF was associated with increased inflammatory response, reduced blood loss, and less blood transfusions in adults undergoing coronary artery bypass grafting.